1. Field of the Invention
The present invention relates to a hearing aid with variable operation modes.
2. Description of the Related Art
In the recent years, digital signal processing is applied in a hearing aid, which enables more complicated signal processing in comparison with an analog hearing aid. However, on the other hand, for digital processing, parts consuming large power, such as DSP (Digital Signal Processor) and CPU (Central Processing Unit) are used in the hearing aid. Therefore, it shortens the duration of continuous operation of the hearing aid.
Therefore, in the hearing aid employing digital signal processing (hereinafter referred to as "digital hearing aid"), there has been proposed a method to reduce power consumption by controlling circuit blocks to be operated depending upon an input voice signal.
FIG. 1 is a circuit diagram showing the conventional digital hearing aid. As shown in FIG. 1, the digital hearing aid is constructed with a microphone 1 which converts a voice signal into an electric signal, an input amplifier 2 amplifying the electric signal, a voice level judgement circuit 3 judging magnitude of amplified signal, a signal processing circuit 4 processing the amplified signal, a changeover switch 5 for selecting the amplified signal of the input amplifier 2 and the processing signal of the signal processing circuit 4, an output amplifier 6 outputting a selection signal, an earphone 7 converting the output signal into the voice signal, a power source 8 driving all of the foregoing circuits, a switch 9a for shutting off power supply for the signal processing circuit 4, and a switch 9b for shutting off the power supply for the output amplifier 6.
When the switches 9a and 9b supply power to the signal processing circuit 4 and the output amplifier 6, the hearing aid amplifies the input signal of the microphone 1 by the input amplifier 2. Then, after signal processing by the signal processing circuit 4, the earphone 7 is driven by the output of the output amplifier 6. The input voice signal level is judged by the voice level judgement circuit 3 to control power supply to the signal processing circuit 4 and the output amplifier 6. Namely, while no voice condition, power supply for both of the signal processing circuit 4 and the output amplifier 6 is shut off. In an ordinary sound field level in normal life, power supply only for the signal processing circuit 4 is shut off. The changeover switch 5 selects the output signal of the input amplifier 2 to supply to the output amplifier 6 so that the earphone 7 is driven by the output signal of the output amplifier 6.
On the other hand, Japanese Unexamined Patent Publication (Kokai) No. Heisei 6-105399 discloses a hearing aid, in which standard patterns representing typical input sounds are preliminarily registered, mutually different hearing compensation methods are provided with respect to respective patterns for selecting hearing compensation methods depending upon the input sound.
However, as set forth above, while the digital hearing aid is advantageous for permitting complicated signal processing, it encounters a problem of short duration in continuous operation for employing parts consuming large amount of power, such as DSP, CPU or so forth.
Japanese Unexamined Patent Publication No. Heisei 5-344595 proposed as a solution for the problem set forth above, merely discloses a hearing aid which varies operation modes depending upon an input voice signal. On the other hand, Japanese Unexamined Patent Publication No. Heisei 6-105399 discloses a hearing aid which merely varies hearing compensation method only depending upon the input voice signal.
Namely, these hearing aids performs switching of the operation modes or hearing compensation methods ignoring condition upon wearing condition or desire of the wearer, and thus cannot vary characteristics adapting to the condition of the wearer. For example, it is possible to be caused a condition where the operation mode or hearing compensation method is not varied for environmental sound being held unchanged, despite that the wearer is in sleeping.